The unconditional guard destructors check whether the lock pointer is NULL before unlocking. This check is dead code because unconditional guards guarantee a non-NULL lock pointer at destructor time. DEFINE_GUARD() runs the lock operation unconditionally in the constructor. If the pointer were NULL, the lock operation (e.g. mutex_lock(NULL)) would crash before the constructor returns. The destructor never runs with a NULL pointer. All DEFINE_GUARD() users dereference the pointer in their lock. Verified by auditing every instance found by: git grep -n -A 1 'DEFINE_GUARD('. The only exception is xe_pm_runtime_release_only, whose constructor is a noop, but it has no callers. __DEFINE_UNLOCK_GUARD() has only a few usages outside of include/linux/cleanup.h: tty_port_tty (NULL-checks in its tty_kref_put() call), irqdesc_lock (fixed earlier) and two guards in kernel/sched/sched.h (dereference the pointer unconditionally in their lock constructors). DEFINE_LOCK_GUARD_1() sets .lock from its argument and runs the lock operation in the constructor. Same reasoning applies. All DEFINE_LOCK_GUARD_1() users dereference the pointer in their lock. Also, verified by auditing every match of: git grep -n 'DEFINE_LOCK_GUARD_1('. DEFINE_LOCK_GUARD_0() hardcodes .lock = (void *)1 in the constructor, so it is never NULL by construction. Conditional (_try) variants: DEFINE_GUARD_COND() and DEFINE_LOCK_GUARD_1_COND() use EXTEND_CLASS_COND(), whose wrapper destructor returns early when the lock was not acquired, before reaching the base destructor since commit 2deccd5c862a ("cleanup: Optimize guards"): if (_cond) return; class_##_name##_destructor(_T); As compiled by GCC-11 with defconfig on top of the locking/core: Total: Before=23889980, After=23834334, chg -0.23% Signed-off-by: Dmitry Ilvokhin --- include/linux/cleanup.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h index 4e60d519713c..65416938e318 100644 --- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -398,7 +398,7 @@ static __maybe_unused const bool class_##_name##_is_conditional = _is_cond #define DEFINE_GUARD(_name, _type, _lock, _unlock) \ static __always_inline __nonnull_args() _type class_##_name##_constructor(_type _T); \ - DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \ + DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T); \ DEFINE_CLASS_IS_GUARD(_name) #define DEFINE_GUARD_COND_4(_name, _ext, _lock, _cond) \ @@ -492,7 +492,7 @@ typedef struct { \ static __always_inline void class_##_name##_destructor(class_##_name##_t *_T) \ __no_context_analysis \ { \ - if (_T->lock) { _unlock; } \ + _unlock; \ } \ \ __DEFINE_GUARD_LOCK_PTR(_name, &_T->lock) -- 2.53.0-Meta